The present invention relates to semiconductor memory devices, and more particularly, to a nonvolatile memory device and a programming method of the same.
Semiconductor memory devices are storage units for storing and retrieving data in accordance with system and/or user requirements. Semiconductor memory devices generally may be classified as random access memories (RAMs) and read-only memories (ROMs). ROMs are able to retain stored data even when there is no power supply. Types of ROMs include, for example, programmable ROMs (PROMs), erasable programmable ROMs (EPROMs), electrically erasable and programmable ROMs (EEPROMs) and flash memories. Flash memories are classified as NAND-type or NOR type flash memory devices. NOR-type flash memory devices operate at higher speeds than NAND-type flash memory devices, which are mostly employed in mobile telephone terminals requiring high frequency data processing.
In order to increase information storage capacity, many studies are underway to address multi-bit cell technology, which enables a single memory cell to store multiple bits. A memory cell capable of storing multiple bits is called a multi-level cell (MLC), as compared to a memory cell capable of storing a single bit, which is called a single level cell (SLC).
An MLC is selectively conditioned in one of multiple possible threshold-voltage distributions. For example, an MLC capable of storing two bits may belong to one of four threshold-voltage distributions (“11”, “10”, “01” and “00”). To read data from such an MLC, the corresponding threshold voltage must be more precisely controlled than the threshold voltage of an SLC.